这题就不用多说了吧

判断一个数是正数、负数还是0，只需要看第一位就好了。

#include<stdio.h>
int main(){
    switch (getchar()) {
        case '-':
            printf("negative");
            return 0;
        case '0':
            printf("zero");
            return 0;
        default:
            printf("positive");
            return 0;
    }
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
long long q,w,e,r,t,y,u,i,o,p,d,f,g,h,j,k,l,z,x,c,v,b,n,m;
string s;
long long a[100000],as[100000],asd[100000];
char cc;
double dd;
int main()
{
	cin>>x;
	if(x>0)
	cout<<"positive";
	if(x==0)
	cout<<"zero";
	if(x<0)
	cout<<"negative";
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a;
    cin>>a;
    if (a == 0)
    {
        cout<<"zero";
        return 0;
    }
    if (a < 0)
    {
        cout<<"negative";
        return 0;
    }
    if (a > 0)
    {
        cout<<"positive";
        return 0;
    }
}

#include <bits/stdc++.h>

using namespace std;

int main() {
	int n;
	cin>>n;
	if (n == 0) {
		printf("zero");
	} else if (n < 0) {
		printf("negative");
	} else {
		printf("positive");
	}
	return 0;
} 

#include<iostream>
#include<cstdio>
using namespace std;
int n;
int main(){
	cin>>n;
	if(n>0) printf("positive\n");
	if(n==0) printf("zero\n");
	if(n<0) printf("negative\n");
	return 0;
}

记录：https://www.luogu.com.cn/record/63710536